This invention relates to guanidines and more particularly to nitroguandine.
Nitroguanidine is a mass detonating explosive. It is a white crystalline powder with a specific gravity of 1.77. Tests conducted at the Naval Ordnance Laboratory in White Oak, Maryland, (Feb. 1968) showed that in its range of detonability, nitroguanidine behaves as a group I Explosive Class 1, Division 1 (Old Class 7), DOT Class A. This means that it is a mass detonating hazard. The entire quantity will explode virtually instantaneously when a small portion is subjected to the impulse of an initiating agent, or to the effect of a considerable discharge of energy from without, or from sympathetic detonation or propagation. Such an explosion normally will cause severe structural damage to adjacent objects and the simultaneous explosion of other separated explosives and ammunition placed sufficiently close to the initially exploding mass. Casting powder, bulk explosives such as TNT, HMX, RDX, and most warheads and bombs are in this class.
Nitroguanidine is a powerful high explosive which when incorporated in a propellant in appreciable quantities, results in a propellant that burns in a gun with a temperature so cool that a little muzzle flash is produced. Nitroguanidine was first prepared by Jousselin in 1877, and found its original application in cool, burning triple-base, Naval gun propellants in trench mortar shells. Its principal use, however, is in smokeless propellant, due to its property of eliminating flash. In later years nitroguanidine has been developed as an ingredient in propellants for rockets and missiles. High bulk density nitroguanidine (HBNQ) is prepared for these later applications.
Nitroguanidine exists in at least 2 crystal forms: an alpha and a beta. The alpha form crystallizes from hot water as long, thin, flexible, lustrous needles which are tough and pulverize with difficulty. It is the form most commonly used in the explosive industry. The beta form crystallizes from hot water in fern-like clusters of small, thin, elongated plates. The beta form may, be converted into the alpha by dissolution in concentrated sulfuric acid and drowning in water.
A communitor with a hammer speed of 7500 RPM is used to reduce the HBNQ particles to desired size. There are two variables to control the particle size: screen size and feed rate. By keeping the screen and hammer speed constant, but changing to a heavier gauge screen, a smaller particle size is achieved. Therefore, when going to heavier gauge screens for greater strength, it is necessary to increase the size of the opening if the same product size is needed. A uniform feed rate is essential for uniform end product. A built-in feeder permits continuous operation and maximum performance. Once the communitor is set to deliver a certain product it will continue to produce exactly the same results. This last step is very labor-consuming and has a high potential for exploding during the crushing and also the drying operations. Also, the convection oven drying of the nitroguanidine releases undesirable organic chemicals into the environment.
Moreover, the HBNQ which is produced by these prior art methods is rodshaped or needleshaped and therefore difficult to use in explosive manufacturing processes such as extrusion and melt casting.
It would be desirable to provide a continuous process for producing round ovate or spheroidal high bulk density nitroguandine crystals.